1. Field of the Invention
A railway vehicle safety shunt system includes a pair of annular axle-mounted rail wheels having outer circumferential surfaces that engage the upper surfaces of the associated rails, respectively, radially outwardly directed flange portions that engage the lateral surfaces of the rails, and central hub portions having end surfaces normal to the axis of rotation of each rail wheel. A pair of collinearly-arranged axially spaced wire brushes are supported between, and parallel with the axes of rotation of, the associated rail wheels, said brushes being spring-biased axially apart into frictional electrical contact with the adjacent hub portion of the associated rail wheel. The brushes are electrically connected together by a shunt conductor, thereby to present an indication of the location of the vehicle at a remotely located vehicle position monitoring and dispatching station.
2. Brief Description of the Prior Art
As shown by the U.S. patents to Bartel, et al., U.S. Pat. No. 5,054,722 and Kruse U.S. Pat. No. 5,464,176, it is well known in the patented prior art to provide shunting devices for indicating the position of a maintenance or inspection railway vehicle on railroad tracks through which electrical monitoring signals are transmitted from a remotely located vehicle position monitoring and dispatching station. In the Bartel et al patent, a wire brush contactor rubs against the rail adjacent the rail guide wheel. Thus, the shunt is automatically engaged when the guide wheels are lowered against the rail. Similarly, in the Kruse patent, the shunting devices are attached to the high rail attachment for making electrical contact with the tracks. Consequently, the brush drags against the track as the maintenance vehicle drives down the track.
Referring to the Powell U.S. Pat. No. 4,488,494, it is also known in the prior art to provide convertible railway inspection and maintenance vehicles having alternately operable resilient wheel and rail wheels for transporting the vehicle along the ground and along the tracks, respectively. Hydraulic motor means are provided for vertically displacing the rail wheels relative to the chassis in order to convert the vehicle for land and rail transport, respectively. Similarly, the Pettibone Corporation of Chicago, Ill. manufactures such a convertible railway vehicle. Applicant is aware that others have proposed to provide a shunt connection between the rail wheels shown in the Powell patent, use being.make of carbon or graphite-containing ceramic contact blocks that frictionally engage the circumferential surfaces of the rail wheels. The contact blocks are electrically connected to define a shunt across the tracks, thereby giving an indication of the instantaneous position of the vehicle. This proposal has the inherent drawback that over time, both the rail wheel circumferential surface and the block contacts tend to chip and become worn through use, thereby affecting the reliability of the shunting operation. Also, mounting of the contact blocks on the vehicle has proven to be rather structurally difficult, making the replacement of the blocks difficult, time-consuming and costly.
The present invention was developed to produce an improved inexpensive and reliable railway shunting system that avoids the above and other drawbacks of the known devices.
Accordingly, a primary object of the present invention is to provide a railway vehicle safety shunting system including a pair of collinearly arranged axially-spaced conductive electrically connected brush members that are arranged between a pair of rail wheels, together with spring means that bias the brush members axially apart into engaged positions in continuous electrical engagement with the adjacent end surfaces of the rail wheels, respectively, whereby when the rail wheels are in engagement with the transport rails, a shunt is automatically established between the rails to provide an instantaneous indication of the location of the vehicle.
According to a more specific object of the invention, the brush contact members are removably connected with support members that are connected with the vehicle for axial displacement relative to the rail wheels, thereby to permit displacement of the support members axially together against the biasing force of the spring means toward retracted positions at which the brush members may be removed from the support means for replacement or repair. According to a further feature, retaining means may be provided for retaining the support and brush members in their retracted positions relative to the rail wheels.
Another object of the invention is to provide shunt means of the type described above that are suitable for use either with railway vehicles having only rail wheels, or with convertible type vehicles having alternately operable resilient wheels and rail wheels. In the latter case, the wire brush members are mounted for axial displacement on the axle cover member that is displaced simultaneously with the rail wheel axle when the rail wheels are displaced by hydraulic motor means between their operable and inoperable positions relative to the resilient wheels.
According to a further object of the invention, the rail wheels each include a cylindrical circumferential surface adapted to ride on the top of the associated rail, a flange that extends radially outward from the circumferential surface for engagement with the sides of the rails, and a pair of end surfaces, the central portion of each wheel having a hub portion that is supported by the wheel bearing means. In the preferred embodiment, the collinearly arranged conductive brushes are so arranged relative to the rail wheel axle that they are biased outwardly into electrical contact with the end wall surfaces of the hub portions of the rail wheels adjacent the wheel bearing means, respectively. According to another embodiment, the brushes engage the adjacent end faces of the rail wheels at opposite locations spaced radially outwardly from the hub portions of the wheels.